GB915254A - Improvements in systems for synchronizing a magnetic tape apparatus with another apparatus - Google Patents

Abstract

915,254. Automatic speed control. AMPEX CORPORATION. April 4, 1961 [April 21, 1960], No. 12061/61. Class 38 (4). In a synchronizing system for a magnetic tape upon which television signals are recorded a reference signal 10 is derived from a local generator during the recording operation and is passed through a sync. separator 12 from which a vertical sync. component is recovered. This component is applied to a phase comparator 14 and to a frequency multiplier 16 developing a sine wave signal. The sine wave signal is applied to a phase shifter 18 which varies the phase of such signal when an error signal is developed at comparator 14. A speed-responsive signal is developed by a photo-cell associated with a scanning-head drum assembly and is applied from terminal 22 to comparator 14. The error signal actuates motor 24 for driving the phase shifter 18, the output of which is coupled to a driving-motor for the scanning drum. The signal from the photo-cell is also applied to frequency discriminator 26 developing a frequency error control signal to control phase modulator 20. During the playback operation, a reference signal from source 28 is channelled to a sync. separator 30 for separation into vertical and horizontal components, the latter having the higher frequency. The vertical component is fed to a frequency multiplier 32 and to a vertical phase comparator 34. The output of the multiplier is applied through phase shifter 36 and phase modulator 38 to control the speed of the motor coupled to the scanning drum. At the same time, a signal is derived from the tape and applied to a sync. separator 40 for separation into vertical and horizontal components, the vertical component being fed to the comparator 34 developing an error signal to actuate relay 42. The relay passes the error signal to the phase shifter 36. The horizontal component derived from the tape is then compared with the horizontal component from the reference source in phase comparator 44, the error signal being applied to modulator 38. This affords small instantaneous corrections for maintaining the angular velocity of the driving- motor and the scanning drum within narrow limits. When the comparator 34 is producing an error signal, the relay 42 connects the comparator 44 to earth, so maintaining the input to the modulator 38 in a steady state condition. A frequency discriminator 46 develops a frequency error signal for controlling the modulator 38.